Lubricating oil composition containing a dispersing-varnish inhibiting combination of an oxazoline compound and an acyl nitrogen compound

ABSTRACT

The combination of an oil-soluble oxazoline reaction product having a (M n ) of from about 1,000 to 3500, e.g., the reaction product of polybutenyl succinic anhydride with tris(hydroxymethyl) aminomethane and an oil-soluble acylated nitrogen compound having a (M n ) of from about 1300 to 8,000, e.g. polybutenyl succinic anhydride reacted with tetraethylene pentamine which nitrogen compound can be borated, if desired, are surprisingly useful as combined additives for lubricating oils to increase the dispersancy and varnish inhibition properties of said oil when one part per weight of said oxazoline reaction product is combined with from 0.2 to 4, preferably 1 to 3, parts by weight of said acylated nitrogen compound.

BACKGROUND OF THE INVENTION

The invention relates to a combination of chemical compositions whichare especially useful in lubricating oil systems. More specifically, itrelates to a combination of an oxazoline oil additive and an imide oiladditive, both of which are known as lubricating oil additives, whichmarkedly improve the sludge dispersancy-varnish inhibiting properties oflubricating oils employed for crankcase lubrication of internalcombustion engines.

There are two principle environments which are encountered by automotivecrankcase lubricants, i.e. cyclical high and low temperatues fromstop-and-go driving and continuous high temperatures from extendedoperation of the automobile over long distances. Each of theseenvironments poses a primary problem which should be solved if alubricant is to be regarded as satisfactory. These problems are theresult of the inevitable presence in the lubricant of varyingproportions of foreign particles such as dirt, soot, water anddecomposition products resulting from breakdown of the oil. This foreignmatter appears responsible for the deposition of a mayonnaise-likesludge which circulates with the oil. The presence of water andprecursors of sludge in lubricating oil seems to depend largely on theoperating temperature of the oil. Although at high temperatures thewater will be evaporated, breakdown of the oil is accelerated. At lowtemperatures, water will accumulate and so consequently will provoke thesludging. In ordinary stop-and-go driving, the crankcase lubricant willbe alternately hot and cold so that the formation of sludge is a seriousproblem.

Another principle problem in addition to the sludge which must beovercome by a satisfactory lubricant is varnish deposition which resultsfrom the operation of the engine at continuous high temperatures. Insuch an environment, oil breakdown results in the formation of acidicmaterials which in themselves corrode the metal surfaces of thebearings, pistons, etc., as well as catalyze the decomposition of thelubricating oil which decomposition is manifested in hard, carbonaceousdeposits which accumulate in the piston ring groove and form a varnishon the piston skirts and other metal surfaces.

During the past decade, ashless sludge dispersants have becomeincreasingly important, primarily in improving the performance oflubricants in keeping the engine clean of deposits and permittingextended crankcase oil drain periods while avoiding the undesirableenvironmental impact of the earlier used metal-containing additives.Most commercial ashless dispersants fall into several generalcategories. In one category, an amine or polyamine is attached to along-chain hydrocarbon polymer (the oil solubilizing portion of themolecule), usually polyisobutylene through an acid group, such as amonocarboxylic acid, for example, see U.S. Pat. No. 3,444,170 or adicarboxylic acid material such as polyisobutenyl succinic anhydride, byforming amide or imide linkages such as described in U.S. Pat. Nos.3,172,892 and 3,272,746 and may include the reaction product of suchmaterials with boron (see U.S. Pat. Nos. 3,087,936 and 3,254,025). Mixedalkenyl succinimides prepared from a high molecular weight and lowmolecular weight alkenyl fraction are taught as lubricant dispersants inU.S. Pat. No. 3,401,118. Mixtures of high molecular weight hydrocarbyl(1900 to 5,000) amines and low molecular weight hydrocarbyl (300 to 600)amines are taught as useful for dispersancy/detergency in hydrocarbonfuels (see U.S. Pat. No. 3,898,056).

Reaction products of hydrocarbon substituted succinic anhydride, e.g.,polyisobutenylsuccinic anhydride, with compounds containing both anamine group and a hydroxy group have been suggested or investigated inthe prior art. For example, United Kingdom Specification 809,001 teachescorrosion inhibitors comprising a multiple salt complex derived from thereaction product of hydrocarbyl substituted dicarboxylic acids andhydroxy amines (including 2-amino-2-methyl-1,3-propanediol [AMP] andtris-(hydroxymethyl)-aminomethane [THAM]. Further, United KingdomSpecification No. 984,409 teaches ashless, amide/imide/ester typelubricant additives prepared by reacting an alkenylsuccinic anhydride,said alkenyl group having 30 to 700 carbon atoms with a hydroxy amineincluding THAM. This prior art appears to teach that oil additives areformed from hydrocarbyl substituted dicarboxylic acid material, usuallyalkenyl succinic anhydride, reacted with various amino or hydroxycompounds either through an amide, imide or ester linkage.

In contrast to the foregoing, German (DOS) 2512201 teaches that thereaction of a hydrocarbyl dicarboxylic acid material, i.e. acid oranhydride, or ester, with certain classes of amino alcohols, undercertain conditions including metal salt promotion, will result inproducts containing one or two heterocyclic ring structures, namely, anoxazoline ring, and that products containing at least one oxazoline ringcan be tailored for various functions, such as anti-rust agents,detergents, or dispersants for oleaginous compositions including lubeoil, gasoline, turbine oils and oils for drilling applications. FurtherDOS 2534921/2 teaches of similar monooxazoline products which can alsobe modified by reaction with phosphorous, boron or oxygen compounds toenhance lubricating oil properties including sludge dispersancy. U.S.Pat. No. 3,966,620 teaches of lubricants containing bis-naphthols asrust inhibitors and the oxazoline reaction product ofpolyalkenylsuccinic acid and THAM as a dispersant.

SUMMARY OF THE INVENTION

As noted above, the prior art teaches that oil-soluble additives of theacylated nitrogen type and the oxazoline type are each useful forlubricating oils.

It has now been found that the combination of an oil-soluble polyalkenyloxazoline compound, having a number average molecular weight of about1000 to 3300, preferably from about 1200 to 3100, optimally from about1600 to 2800, preferably polybutenyl succinic-bis-oxazoline (obtainedfrom the reaction of polybutenyl succinic anhydride andtris(hydroxymethyl) aminomethane) and an oil-soluble acyl nitrogencompound having a number average molecular weight of about 1300 to8,000, preferably about 2,000 to 6,000, optimally 3,000 to 5,000,preferably polybutenyl succinimide (obtained from the reaction ofpolybutenyl succinic anhydride and one molar equivalent of e.g.tetraethylene pentamine) alkylene polyamine exhibits synergisticbehavior in dispersancy and/or varnish inhibition when employed in aratio of one part per weight of the oxazoline compound to from 0.2 to 4,preferably 1 to 3 parts, by weight of the acyl nitrogen compound whensaid combination is present in at least a dispersing amount in alubricating oil.

Thus in its broadest concept, the subject matter of the invention is alubricating oil composition comprising a major amount of lubricating oiland a minor but dispersing amount of a dispersing varnish inhibitingcombination of: (a) one part by weight of an oil-soluble oxazolinereaction product having a number average molecular weight (hereinafterdesignated (M_(n))) of from about 1000 to about 3300 obtained from thereaction of one molar proportion of a hydrocarbyl substituted C₄ -C₁₀monounsaturated dicarboxylic acid material and from about 1.5 to abut 2molar proportions of a 2,2-disubstituted-2-amino-1-alkanol having 2 to 3hydroxy groups and containing a total of 4 to 8 carbons and representedby the formula: ##STR1## wherein X is an alkyl, or hydroxy alkyl group,with at least one of the X substituents being a hydroxy alkyl group ofthe structure --(CH₂)_(n) OH, wherein n is 1 to 3; and, (b) from 0.2 to4 parts by weight of an oil-soluble acyl nitrogen compound having a(M_(n)) of from about 1300 to 8000 characterized by the presence withinits structure of a substantially saturated hydrocarbon-substituted polargroup selected from the class consisting of acyl, acylimidoyl, andacyloxy radicals wherein the substantially saturated hydrocarbonsubstituent contains at least about 50 aliphatic carbon atoms and anitrogen-containing group characterized by a nitrogen atom attacheddirectly to said polar radical.

In preferred form, the combination is limited to said oxazoline productand nitrogen compound wherein both are derived from hydrocarbylsubstituted dicarboxylic acid materials wherein said hydrocarbylsubstituent has a (M_(n)) ranging from about 900 to 2800, optimallyabout 1200 to 2500, i.e. both the acylated nitrogen compound and theoxazoline product are derived therefrom.

DETAILED DESCRIPTION OF THE INVENTION

The hydrocarbyl substituted dicarboxylic acid material, i.e., acid oranhydride, or ester which is used to produce both classes of dispersantsincludes alpha-beta unsaturated C₄ to C₁₀ dicarboxylic acid, oranhydrides or esters thereof, such as fumaric acid, itaconic acid,maleic acid, maleic anhydride, chloromaleic acid, dimethyl fumarate,etc., which are substituted with a hydrocarbyl group, usefully ahydrocarbon chain containing at least 50 carbons (branched orunbranched) and includes long hydrocarbon chains, generally an olefinpolymer chain.

In general, these hydrocarbyl substituted dicarboxylic acid materialsand their prepartion are well known in the art, for example see U.S.Pat. Nos. 3,219,666; 3,172,892; 3,272,746; the aforementioned prior artpatents; as well as being commercially available, e.g., polyisobutylenesuccinic anhydride.

The dicarboxylic acid material can be illustrated by an alkenylsubstituted anhydride which may contain a single alkenyl radical or amixture of alkenyl radicals variously bonded to the cyclic succinicanhydride group, and is understood to comprise such structures as:##STR2## wherein R is hydrogen or lower hydrocarbyl and R₁ ishydrocarbyl or substituted hydrocarbyl having from 50 to about 400 andmore carbons, and preferably from 65 to about 200 carbons. Theanhydrides can be obtained by well-known methods, such as the Enereaction between an olefin and maleic anhydride or halo-succinicanhydride or succinic ester (U.S. Pat. No. 2,568,876). In branchedolefins, particularly branched polyolefins, R may be hydrogen or methyland R₁ at least a C₅₀ long chain hydrocarbyl group. However, the exactstructure may not always be ascertained and the various R and R₁ groupscannot always be precisely defined in the Ene products from polyolefinsand maleic anhydride.

Suitable olefins include butene, isobutene, pentene, decene, dodecene,tetradecene, hexadecene, octadecene, eicosene, and polymers ofpropylene, butene, isobutene, pentene, decene and the like, andhalogen-containing olefins. The olefins may also contain cycloalkyl andaromatic groups.

With 2-chloromaleic anhydride and related acylating agents,alkenylmaleic anhydride reactants are formed. Derivatization of thesereactants also afford useful imide or oxazoline products.

Preferred olefin polymers for reaction with the unsaturated dicarboxylicacids are polymers comprising a major molar amount of C₂ to C₅monoolefin, e.g., ethylene, propylene, butylene, isobutylene andpentene. The polymers can be homopolymers such as polyisobutylene, aswell as copolymers of two or more of such olefins such as copolymers of:ethylene and propylene; butylene and isobutylene; propylene andisobutylene; etc. Other copolymers include those in which a minor amountof the copolymer monomers, e.g., 1 to 20 mole % is a C₄ to C₁₈non-conjugated diolefin, e.g., a copolymer of isobutylene and butadiene;or a copolymer of ethylene, propylene and 1,4-hexadiene; etc.

The olefin polymers will usually have (M_(n))s within the range of about700 and about 3,000, more usually between about 900 and about 2800.Particularly useful olefin polymers have (M_(n))s of about 1200 to 2500with approximately one terminal double bond per polymer chain. Anespecially valuable starting material for a highly potent dispersantadditive are polyalkenes e.g., polyisobutylene, having about 80 carbons.

OIL-SOLUBLE OXAZOLINE REACTION PRODUCT

Generally, useful oil-soluble oxazoline reaction products and theirmethods of preparation are fully described in German Patent ApplicationDOS 2512201 which is fully incorporated herein by reference thereto.This oxazoline dispersant which forms a portion of the inventivecombination can be characterized in its preferred form as an oil-solubleproduct obtained from heating together a molar equivalent of ahydrocarbon substituted C₄ -C₁₀ mono-unsaturated dicarboxylic acidmaterial having more than about 50 carbon atoms per dicarboxylic acylgroup and from 1.5 to about 2 molar equivalents of a2,2-disubstituted-2-amino-1-alkanol having 2 to 3 hydroxy groups andcontaining a total of 4 to 8 carbons at a temperature of from about 140°C. to 240° C. until cessation of water evolution indicating completionof the oxazoline reaction. This reference amino-alkanol which readilyproduces the oxazoline rings requisite for this dispersant according tothis invention can be represented by the formula ##STR3## wherein X isan alkyl, or hydroxy alkyl group, with at least one of the Xsubstituents being a hydroxy alkyl group of the structure -(CH₂)_(n) OH,wherein n is 1 to 3.

Examples of such 2,2-disubstituted amino-alkanols, include2-amino-2-methyl-1,3-propanediol,2-amino-2-(hydroxymethyl)-1,3-propanediol (also known astris(-hydroxymethyl-)aminomethane or THAM),2-amino-2-ethyl-1,3-propanediol, etc. Because of its effectiveness,availability, and cost, the THAM is particularly preferred. It is to benoted that other amino alcohols such as ethanolamine, propanolamine andbutanolamine which lack the 2,2-disubstitution, do not afford theoxazoline product. The requisite (M_(n)) ranges of these products havealready been specified.

The formation of the preferred oxazoline dispersants in high yield, canbe effected by adding about 1.5 to 2 mole equivalent of the aforesaid2,2-disubstituted-2-amino-1-alkanol per mole equivalent of thedicarboxylic acid material, with or without an inert diluent, andheating the mixture at 140°-240° C., optimally 170°-220° C. andpreferably 180°-205° C. for 1/2 to 24, more usually 2 to 8 hours, untilthe reaction is complete.

Completion of the oxazoline reaction can be readily ascertained by usingperiodic infrared spectral analysis for following oxazoline formation(oxazoline peak forms at 6.0 microns), or by the cessation of waterevolution of about 2.3 to 3.0 moles of water.

Although not necessary, the presence of small amounts, such as 0.01 to 2wt. %, preferably 0.1 to 1 wt. % based on the weight of the reactants,of a metal salt can be used in the reaction mixture as a catalyst. Themetal catalyst can be later removed by filtration or by washing ahydrocarbon solution of the product with a lower alcohol, such asmethanol, ethanol, isopropanol, etc., or an alcohol/water solution.

Alternatively, the metal salt can be left in the reaction mixture, as itappears to become stably dispersed, or dissolved, in the reactionproduct and depending on the metal, it can contribute performancebenefits to the lubricating oil. This is believed to occur with the useof zinc catalysts in lubricants.

Inert solvents which may be used in the oxazoline reaction includehydrocarbon oils, e.g., mineral lubricating oil, kerosene, neutralmineral oils, xylene, halogenated hydrocarbons, e.g., carbontetrachloride, dichlorobenzene, tetrahydrofuran, etc.

Metal salts that may be used as promoters or catalysts includecarboxylic acid salts of Zn, Co, Mn, Ni and Fe. Metal catalysts derivedfrom strong acids (HCl, sulfonic acids, H₂ SO₄), HNO, etc.) and basestend to diminish the yield of the oxazoline products and instead favorimide or ester formation. For this reason, these strong acid salts orbasic salts are not preferred and usually will be avoided. Thecarboxylic acids used to prepare the desired promoters include C₁ toC₁₈, e.g., C₁ to C₈ acids, such as the saturated or unsaturated mono-and dicarboxylic aliphatic hydrocarbon acids, particularly fatty acids.Specific examples of such desired carboxylic acid salts include zincacetate, zinc formate, zinc propionate, zinc stearate, manganese(ous)acetate, iron tartarate, cobalt(ous) acetate, nickel acetate, etc. Zincsalts such as zinc acetate and zinc oxide, are preferred. Metal saltsinclude the oxides.

It is preferred that the metal salt promoter be present at or near theonset of the reaction for greatest effect. The zinc salt promotergradually dissolves by forming, inter alia, zinc complexes with theoxazoline product. Significantly and unexpectedly, the presence of zincin the oxazoline product apparently contributes performance benefits tothe lubricating oil.

While not known with complete certainty, it is believed that thereaction of the hydrocarbyl substituted dicarboxylic acid material,e.g., a substituted succinic anhydride with the amino alcohol of theinvention, e.g., about 1.5 to 2 equivalents of2,2-disubstutitued-2-amino-methanol such astris-hydroxymethylaminomethane (THAM), gives oxazoline, e.g. a mixtureof monooxazoline and bis-oxazoline to all bis-oxazoline via theintermediacy of several discrete reaction species. If an acid anhydrideis used, the initial transformation appears to involve the scission ofthe anhydride by the amino function of one mole of the amino alcohol toyield an amic acid. Addition of another mole equivalent of amino alcoholis believed to form the amic acid amine salt, which then upon furtherheating, undergoes cyclodehydration to the final bis-oxazoline product.

The promoting effect of metal salts, such as zinc acetate (ZnAc₂), onoxazoline formation is very likely ascribable to the favorablepolarization of the amide group by the zinc salt towards attack by thehydroxy function of the amino alcohol reactant. It is believed that thedissolved zinc salt ultimately coordinates with the oxazoline ring.

ACYL NITROGEN COMPOUND

The acyl nitrogen compound is of that class of oil-soluble dispersantsbroadly described in U.S. Pat. No. 3,272,746 (it is incorporated hereinby reference thereto) as an oil-soluble acylated nitrogen compoundcharacterized by the presence within its structure of a substantiallysaturated hydrocarbon-substituted polar group selected from the classconsisting of acyl, acylimidoyl, and acyloxy radicals wherein thesubstantially saturated hydrocarbon substituent contains at least about50 aliphatic carbon atoms and a nitrogen-containing group characterizedby a nitrogen atom attached directly to said polar radical. For thepurposes of this invention, these acyl nitrogen compounds have a (M_(n))ranging from about 1300 to 8000, preferably from about 2000 to 6000 andoptimally from about 3000 to 5000. All (M_(n)) values set forth in thisspecification have been determined by Vapor Pressure Osmometry (VPO).

The relative polar groups of the acyl nitrogen compound are representedby the structural configurations as follows: ##STR4## where R₃ is thesubstantially saturated hydrocarbon substituent extensively discussedearlier as the hydrocarbyl (including the preferred alkenyl) substituentof the dicarboxylic acid material and R₄ represents a hydrogen radicalor a hydrocarbyl group (including polar substituted hydrocarbyls, e.g.C1 substituted).

The nitrogen-containing group of the acylated nitrogen compositions ofthis invention is derived from compounds characterized by a radicalhaving the structural configuration ##STR5## the two reamining valencesof the nitrogen atom of the above ##STR6## radical preferably aresatisfied by hydrogen, amino, or organic radicals bonded to saidnitrogen atom through direct carbon-to-nitrogen linkages. Thus, thecompounds from which the nitrogen-containing group may be derivedinclude aliphatic amines, aromatic amines, heterocyclic amines orcarbocyclic amines. The amines may be primary or secondary amines andpreferably are polyamines such as alkylene amines, arylene amines,cyclic polyamines, and the hydroxy-substituted derivatives of suchpolyamines.

The preferred acyl nitrogen compounds are essentially described as theimides and diimides, preferably diimides, resulting from the reaction of1 to 2.5, preferably about 2.0 to 2.2, molar proportions of thedicarboxylic acid material with one molar proportion of a nitrogencompound having one or more amino groups. Such a preferred compound canbe represented by the structural formula ##STR7## X is a number from 0to 5, etc., when 2 molar proportions of the dicarboxylic acid materialis reacted with one molar proportion of said nitrogen compound havingone or more amine groups and R₁ is the same as earlier defined.

Useful nitrogen compounds include mono- and polyamines of about 2 to 60,e.g. 3 to 20 total carbon atoms and about 1 to 12, e.g. 2 to 6 nitrogenatoms in the molecule. The amine compounds may be hydrocarbyl amines ormay include hydroxy groups, alkoxy groups, amide groups or may be cyclicin structure such as imidazolines and the like. Preferred amines both asnoted above generally and for preparation of said imides and diimidesare aliphatic, saturated amines including those of the general formulae:##STR8## wherein R, R' and R" are independently selected from the groupconsisting of hydrogen; C₁ to C₁₂ straight or branched chain alkylradicals; C₁ to C₁₂ alkoxy C₂ to C₆ alkylene radicals; C₂ to C₁₂ hydroxyor amino alkylene radicals; and C₁ to C₁₂ alkylamino C₂ to C₆ alkyleneradicals; s is a number of from 2 to 6, preferably 2 to 4; and t is anumber of from 0 to 10, preferably 2 to 6.

Non-limiting examples of suitable amine compounds include: mono- and di-tallow amines; 1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane;1,6-diaminohexane; diethylene triamine; triethylene tetramine,tetraethylene pentamine; 1,2-propylene diamine; di-(1,2-propylene)triamine, di-(1,3-propylene) triamine, N,N-dimethyl-1,3-diaminopropane;N,N-di-(2-aminoethyl) ethylene diamine;N,N-di-(2-hydroxyethyl)-1,3-propylene diamine; 3-dodecyloxypropylamine;N-dodecyl-1,3-propane diamine; tris-hydroxymethyl methylamine,diisopropanol amine, and diethanol amine.

Other useful amine compounds include: alicyclic diamines such as1,4-bis-(aminomethyl) cyclohexane, and heterocyclic nitrogen compoundssuch as imidazolines and N-aminoalkyl piperazines of the generalformula: ##STR9## wherein G is independently selected from the groupconsisting of hydrogen and Ω aminoalkylene radicals of from 1 to 3carbon atoms; and p is an integer of from 1 to 4. Non-limiting examplesof such amines include 2-pentadecyl imidazoline; N-(2-aminoethyl)piperazine; N-(3-aminopropyl) piperazine; and N,N'-di-(2-aminoethyl)piperazine.

Commercial mixtures of amine compounds may advantageously be used. Forexample, one process for preparing alkylene amines involves the reactionof an alkylene dihalide (such as ethylene dichloride or propylenedichloride) with ammonia, which results in a complex mixture of alkyleneamines wherein pairs of nitrogens are joined by alkylene groups, formingsuch compounds as diethylene triamine, triethylenetetramine,tetraethylene pentamine and isomeric piperazines. Low costpoly(ethyleneamines) compounds having a composition approximatingtetraethylene pentamine (used for the preparation of the acyl nitrogencompounds of the subsequent Examples herein) are available commerciallyunder the trade name Polyamine 400 (PA-400), marketed by JeffersonChemical Co., New York, NY. Similar material may be made by thepolymerization of aziridine, 2-methyl aziridine and acetidine.

Still other amines with amino groups separated by hetero atom chainssuch as polyethers or sulfides can be used.

Amination of the dicarboxylic acid material is usefully carried in asolution reaction with the dicarboxylic acid material dissolved in asolvent such as mineral oil. The formation of the imide dispersants inhigh yield can be effected by adding from about 0.4 to 1, preferablyabout 0.45 to 0.5, molar proportions of alkylene polyamine per molarproportion of dicarboxylic acid material of the nitrogen compound tosaid solution and heating the mixture at 140° C. to 165° C. until theappropriate amount of water of reaction is evolved.

In some applications, it is useful to modify the acyl nitrogendispersant by subsequent boration as generally taught in U.S. Pat. Nos.3,087,936 and 3,254,025 (incorporated herein by reference thereto). Thisis readily accomplished by treating said acyl nitrogen dispersant with aboron compound selected from the class consisting of boron oxide, boronhalides, boron acids and esters of boron acids in an amount to providefrom about 0.1 atomic proportion of boron for each mole of said acylatednitrogen composition to about 10 atomic proportions of boron for eachatomic proportion of nitrogen of said acylated nitrogen composition.Usefully the dispersants of the inventive combination contain from about0.3 to 0.9 wt. % boron based on the total weight of said borated acylnitrogen compound. The boron, which appears to be in the product asdehydrated boric acid polymers (primarily (HBO₂)₃), attaches chemicallyto the dispersant imides and diimides as amine salts e.g. the metaboratesalt of said diimide.

Treating is readily carried out by adding from about 1 to 3 wt. % (basedon the weight of said acyl nitrogen compound) of said boron compound,preferably boric acid which is most usually added as a slurry to saidacyl nitrogen compound and heating with stirring and at from about 135°C. to 165° C. for from 1 to 5 hours followed by nitrogen stripping atsaid temperature ranges. Filter the borated product, if desired.

THE OXAZOLINE REACTION PRODUCT AND ACYL NITROGEN COMPOUND COMBINATION

The combination of oil-soluble dispersants according to the inventioncan be incorporated in a wide variety of lubricants. They can be used inlubricating oil compositions, such as automotive crankcase lubricatingoils, automatic transmission fluid, etc., in concentrations generallywithin the range of about 0.05 to 10 wt. %, for example, 0.5 to 5 wt. %,preferably 1.5 to 3 wt. % of the total composition. As noted, ingeneral, the additive combination of the invention will comprise onepart by weight of the oxazoline reaction product per about 0.2 to 4,preferably 1 to 3, optimally 2 to 3 parts by weight of said acylnitrogen compound. The lubricating oil to which the synergisticcombination can be added include not only hydrocarbon oils derived frompetroleum but also includes synthetic lubricating oils such aspolyethylene oils; alkyl esters of dicarboxylic acids; complex esters ofdicarboxylic acid, polyglycol and alcohol; alkyl esters of carbonic orphosphoric acids; polysilicones; fluorohydrocarbon oils; and, mixturesof lubricating oils and synthetic oils in any proportion, etc. The term"lubricating oil" for this disclosure includes all the foregoing. Theuseful combination may be conveniently dispensed as a concentrate of 10to 80 wt. % of said synergistic combination in 20 to 90 wt. % of mineraloil, for example, kerosene, with or without other additives beingpresent. In the above compositions or concentrates, other conventionaladditives may also be present including dyes, pour point depressants,antiwear agents such as tricresyl phosphate or zinc dialkyldithiophosphates of 3 to 8 carbon atoms in the alkyl groups,antioxidants such as n-phenylalpha-naphthylamine, tertiary-octyl phenolsulfide, and 4,4'-methylene bis(2,6-di-tert. butyl phenol), viscosityindex improvers such as ethylene-propylene copolymers,polymethacrylates, polyisobutylene, alkyl fumarate-vinyl acetatecopolymers and the like, de-emulsifiers such as polysiloxanes,ethoxylated polymers and the like.

It has been noted that in those combinations of the oxazoline reactionproduct and acyl nitrogen compounds according to this invention thatwhen the (M_(n)) of said oxazoline is about 30% to 60% of the (M_(n) )acyl nitrogen compound exceptionally potent dispersant-varnishinhibition is imparted to the lubricating oil, e.g. (M_(n)) of ˜ 1700for the oxazoline and ˜ 3400 for the acyl nitrogen.

This invention will be further understood by reference to the followingexamples, which include preferred embodiments of the invention.

EXAMPLE 1

A mixture of 500 gm. (0.4 moles) of polyisobutenyl succinic anhydridehaving a Saponification No. of 89 and a (M_(n)) of 980, 500 ml. ofmineral lubricating oil (Solvent 150 Neutral) as solvent, 4 gm. of zincacetate dihydrate (ZnAc.2H₂ O) as a promoter and 96.8 gm. (0.8 mole) ofTHAM was charged into a glass reactor fitted with thermometer, stirrerand a Deane-Starke moisture trap, and heated. Heating at about 180° C.for four hours gave the expected quantity of water, i.e., about 1.1moles of water in the trap. After filtration and rotoevaporation, theconcentrate (50 wt. % of the reaction product) analyzed for 1.00 wt. %nitrogen, and 0.06 wt. % zinc. The product had a (M_(n)) of about 1400.

The polyisobutenylsuccinic anhydride used herein (also used in Example2) was prepared by conventional technique, namely the reaction ofchlorinated polyisobutylene having a chlorine content of about 3.5 wt.%, based on the weight of chlorinated polyisobutylene, and an average of70 carbon atoms in the polyisobutylene group, with maleic anhydride atabout 200° C.

EXAMPLE 2

A borated derivative of the reaction product of polyisobutenyl succinicanhydride and an alkylene polyamine was prepared by first condensing 2.1moles of polyisobutenyl succinic anhydride, having a SaponificationNumber of 89 and a (M_(n)) of 980, dissolved in Solvent Neutral 150mineral oil to provide a 50 wt. % solution with 1 mole of tetraethylenepentamine (hereafter noted as TEPA). The polyisobutenyl succinicanhydride solution was heated to about 150° C. with stirring and thepolyamine was charged into the reaction vessel over a 4-hour periodwhich was thereafter followed by a 3-hour nitrogen strip. Thetemperature was maintained from about 140° C. to 165° C. during both thereaction with the TEPA and the subsequent stripping. While the resultingimidated product was maintained at a temperature of from about 135 toabout 165° C. a slurry of 1.4 moles of boric acid in mineral oil wasadded over a 3-hour period which was thereafter followed by a final4-hour nitrogen strip. After filtration and rotoevaporation, theconcentrate (50 wt. % of the reaction product) contained about 1.5 wt. %nitrogen and 0.3 wt. % boron. The product had a (M_(n)) of about 2420.

EXAMPLE 3

In the same manner as Example 2, 2.1 moles of polyisobutenyl succinicanhydride (Sap. No. of 103 and an M_(n) of about 1300) was utilized inplace of the polyisobutenyl succinic anhydride of Example 2. Theresulting concentrate (50 wt. % active ingredient) analyzed for 1.46%nitrogen and 0.32% boron.

EXAMPLE 4

The general process of Example 1 was used, however in this instance, onemole of polyisobutenyl succinic anhydride (having a SaponificationNumber of 103 and a (M_(n)) of 1300) dissolved to 50 wt % in S150Neutral mineral oil was heated with 0.036 moles of zinc acetatedihydrate and 1.9 moles of THAM at a temperature of from 168° to 174° C.At the end of the THAM addition, the reaction mixture is sparged withnitrogen at 177° C. for 10 hours. After rotoevaporation, the concentrate(50 wt. % active ingredient) analyzed for 1.0 wt. % nitrogen and 0.1 wt.% zinc. The product had a (M_(n)) of about 1700.

EXAMPLE 5

The general process of Example 2 was used, however 1.3 moles ofpolyisobutenyl succinic anhydride was used and boration was notundertaken. The (M_(n)) of the product was about 1520.

EVALUATION OF COMBINATIONS IN VARNISH INHIBITION TEST

Each test sample consisted of 10 grams of lubricating oil containing0.07 of a gram of the additive concentrate (50% active) which results ina total of 0.35 wt. % additive present in the test sample. The test oilto which the additive is admixed was 9.93 grams of a commerciallubricating oil obtained from a taxi after 2,000 miles of driving withsaid lubricating oil. Each ten gram sample was heat soaked overnight atabout 140° C. and thereafter centrifuged to remove the sludge. Thesupernatant fluid of each sample was subjected to heat cycling fromabout 150° C. to room temperature over a period of 3.5 hours at afrequency of about 2 cycles per minute. During the heating phase, thegas containing a mixture of about 0.7 volume percent SO₂, 1.4 volumepercent NO and balance air was bubbled through the test samples andduring the cooling phase water vapor was bubbled through the testsamples. At the end of the test period, which testing cycle can berepeated as necessary to determine the inhibiting effect of anyadditive, the wall surfaces of the test flasks in which the samples werecontained are visually evaluated as to the varnish inhibition. Theamount of varnish imposed on the walls is rated at values of from 1 to 7with the higher number being the greater amount of varnish. It has beenfound that this test correlates with the varnish results obtained as aconsequence of carrying out an MSVC engine test. The results which arerecorded in Table I indicate that combinations of the oxazoline reactionproduct and the acyl nitrogen compound exhibit enhanced behavior whentheir weight ratios range from about one part by weight of the acylnitrogen compound to from 0.2 to 3 parts by weight of the oxazolinecompound; with a synergistic result when the polalkenyl substituent ofeach has a (M_(n)) of about 1300 and about 3 parts by weight of the acylnitrogen compound is combined with 1 part by weight of the oxazolinereactant.

                  TABLE I                                                         ______________________________________                                        Weight Percent of Additive Added to Test Oil                                  Test                                                                          Sam- Additive of                                                                             Additive of                                                                             Additive of                                                                           Additive of                                                                           VIB                                  ple  Example 2 Example 3 Example 4                                                                             Example 5                                                                             Rating                               ______________________________________                                        1    0.35      --        --      --      6                                    2    0.26      --        0.09    --      5                                    3    0.18      --        0.18    --      4                                    4    0.09      --        0.26    --      5                                    5    --        --        0.35    --      7                                    6    --        0.35      --      --      5.5                                  7    --        0.26      0.09    --      3                                    8    --        0.18      0.18    --      4                                    9    --        0.09      0.26    --      5                                    10   --        --        0.35    --      6                                    11   --        --        --      0.35    7                                    12   --        --        0.09    0.26    7                                    13   --        --        0.18    0.18    5                                    14   --        --        0.26    0.09    5                                    15   --        --        0.35    --      6                                    ______________________________________                                    

EXAMPLE 6

Three fully formulated lubricating oil blends were prepared by blendingfive volume percent of the concentrate of Example 1, five volume percentof the concentrate of Example 2 and five volume percent of a 50/50mixture of the concentrate of Example 1 and Example 2, respectively,with a SAE 30 lubricating oil of Solvent 450 N base stock containingabout 0.6 wt. % zinc dialkyl dithiophosphate (hereafter noted as ZDDP)and 0.6 wt. % calcium phenate sulfide.

Each of the blends prepared as described above was subjected to the MSSequence VC Engine Test which is a test well known in the automotiveindustry. The test is run in a Ford engine of 302 cubic inchdisplacement following the procedure described in the publicationentitled "Multi-Cylinder Test Sequences for Evaluating Automotive EngineOil" (ASTM Special Publication 315-E). At the end of each test, variousparts of the engine are rated on a merit basis wherein 10 represents aperfectly clean part, and lesser numbers represent increasing degrees ofdeposit formation. The various ratings are then totaled and averaged onthe basis of 10 as a perfect (completely clean) rating. The resultsobtained with the three blends described above are given in Table II.

                  TABLE II                                                        ______________________________________                                         MS SEQUENCE VC TEST RESULTS                                                  MERIT RATINGS (BASIS 10)                                                                   Additive of the                                                               Concentrate of Example                                                        1       2         1:2                                            ______________________________________                                        Sludge Merit   8.89      9.43      9.14                                       Varnish Merit  7.76      7.97      7.70                                       Piston Skirt   7.68      8.04      8.42                                       Varnish Merit                                                                 ______________________________________                                    

The results set forth above show that synergism does exist for a 50/50mixture of an oxazoline reaction product and an acyl nitrogen dispersantcompound in the merit ratings of the piston skirt varnish. These resultswhen viewed in concert with the data of Tables III and IV indicates thatthe optimum range of this combination is from about 1 to 3 parts byweight of acyl nitrogen dispersant to 1 part by weight of oxazolinereaction product.

EXAMPLE 7

Three fully formulated lubricating oil blends were prepared comparableto those set forth in Example 6 except that the two combined dispersantswere both prepared from polyisobutylene succinic anhydride in which the(M_(n)) of the hydrocarbyl substituent is about 1300 rather than 980,i.e. the additives of Examples 3 and 4 are combined. These three blendswere prepared by blending 5 wt. % of the concentrate of Example 3, 5 wt.% of the concentrate of Example 4 and 5 wt. % of a mixture of thecombination of the concentrates of Examples 3 and 4 (2 wt. parts of Ex.3 to 1 wt. part of Ex. 4), respectively, with a lubricating oil blend oftwo neutral base oils and formulated with about 0.79 wt. % of metaldetergent (calcium sulfonate overbased to a 400 TBN), 0.66 wt. % zincdialkyl dithiophosphate and 0.12 wt. % isoprene-styrene polymerviscosity index improver to provide a fully formulated SAE 10W-40lubricating oil.

The results of the MS Sequence VC Engine Test on the severalformulations are set forth in Table III. TBN represents total basenumber and refers to the milligrams of KOH required to neutralize a onegram sample according to ASTM Method D-2896.

                                      TABLE III                                   __________________________________________________________________________     MS SEQUENCE VC TEST RESULTS                                                  MERIT RATINGS (BASIS 10)                                                                     5 Wt.% of       5 Wt.%      4.0 Wt.%                                          2 pts.          2 pts.                                                                             4.5 Wt.% of                                                                          2 Pts.                                            Concn.          Concn.                                                                             2 Parts                                                                              Concn.                                            Ex. 2           of Ex. 3                                                                           Concn. 3                                                                             Ex. 3                                        5.0 Wt.%                                                                           and 1 Part                                                                          5.0 Wt.%                                                                           5.0 Wt.%                                                                           to 1 Pt.                                                                           to 1 Pt.                                                                             to 1 Pt.                                     Concn.                                                                             of Concn.                                                                           Concn. of                                                                          Concn. of                                                                          Concn.                                                                             Concn. Concn.                                       of Ex. 2                                                                           Ex. 4 Ex. 3                                                                              Ex. 4                                                                              of Ex. 4                                                                           of Ex. 4                                                                             Ex. 4                              __________________________________________________________________________    Sludge    8.00 8.54  8.14 7.66 9.39 8.89   8.14                               Ave. Varnish                                                                            7.68 8.13  8.21 8.62 8.50 8.18   8.45                               Piston Skirt Varnish                                                                    7.64 8.16  7.80 8.09 8.80 8.17   7.86                               __________________________________________________________________________     Concn. represents Concentrate.                                           

The data of Table II shows that the combination of dispersants hassynergistic activity in the MS VC Engine Test both as to sludge meritand piston skirt varnish merit ratings.

EXAMPLE 8

The merit ratings realized from a MS Sequence VC Engine Test on theoptimum combination of the invention shows that the combination includesa ratio ranging between 1 part of the oxazoline reaction product to 2 to3 parts by weight of the acyl nitrogen compound (dispersants are derivedfrom a polyisobutenylsuccinic anhydride having a hydrocarbyl substituentof (M_(n)) of about 1300). The additives were incorporated into a SAE 30lubricating oil of blended neutral distillate and bright stock modifiedwith about 0.4 wt. % magnesium sulfonate, 0.1 wt. % calcium phenatesulfide and 0.6 wt. % zinc dialkyl dithiophosphate. The respective meritratings are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        MS SEQUENCE VC TEST RESULTS                                                   MERIT RATINGS (BASIS 10)                                                                     4 wt. %                                                                       Combination   3 wt. parts                                                     2 wt. parts   Concn. Ex. 3                                     4 Wt. %        Ex. 3 to 1 wt. part                                                                         to 1 wt. part                                    Concn.* Ex. 4  Concn.* of Ex. 4                                                                            Concn.* of Ex. 4                                 ______________________________________                                        Sludge 8.4         9.1           8.7                                          Average                                                                              7.3         8.1           8.0                                          Varnish                                                                       Piston 7.6         8.0           8.0                                          Skirt                                                                         Varnish                                                                       ______________________________________                                         *Indicates a 50 wt.% active ingredient Concentrate.                      

A highly useful concentrate according to this invention is about 50 wt.% diluent as a neutral mineral oil, e.g. S150N, and 50 wt. % of theinvention combination in preferred form i.e. the products of Examples 3and 4 in a weight ratio of one part of said oxazoline reaction productand one to three parts of said acyl nitrogen compound. Such aconcentrate can be represented thus by about 50 wt. % of mineral oildilute, about 17% of the bis-oxazoline of poly(isobutenyl) succinicanhydride wherein said poly(isobutenyl) has a (M_(n)) of about 1300 andabout 33 wt. % of borated tetraethylene pentamino-diimide ofpoly(isobutenyl) succinic anhydride wherein said poly(isobutenyl) has a(M_(n)) of about 1300 and said concentrate contains about 1.3 wt. %nitrogen and about 0.2 wt. % boron. The oxazoline dispersant in usefulform for this disclosure can be generally termed a bisoxazoline since atleast about 60% of the ##STR10## groups of the dicarboxylic acidmaterial have been incorporated into the oxazoline structure.

It is to be understood that the examples present in the foregoingspecification are merely illustrative of this invention and are notintended to limit it in any manner, nor is the invention to be limitedby any theory regarding its operability. The scope of the invention isto be determined by the appended claims.

It is possible to provide some or all of the boron, i.e. up to about0.03 wt. % in lubricating oils is useful for varnish inhibition, to theinventive combination by means of a borated oxazoline reaction compoundproduced according to the general teachings of DOS 2534921 and 2534922.The oxazoline product can contain from about 0.3 to 0.9 wt. % boron.

The inventive combination also provides rust inhibition properties toformulated lubricating oils generally superior to comparable amounts ofknown acyl nitrogen dispersants.

What is claimed is:
 1. A lubricating oil composition comprising a majoramount of lubricating oil and a minor but dispersing amount of adispersing and varnish inhibiting combination of: (a) one part by weightof an oil-soluble oxazoline reaction product having a number averagemolecular weight of from about 1,000 to about 3,300 obtained from thereaction of one molar proportion of a hydrocarbyl substituted C₄ -C₁₀monounsaturated dicarboxylic acid material wherein said hydrocarbylsubstituent contains at least 50 aliphatic carbon atoms, and from about1.5 to about 2 molar proportions of a2,2-disubstituted-2-amino-1-alkanol having 2 to 3 hydroxy groups andcontaining a total of 4 to 8 carbons and represented by the formula:##STR11## wherein X is an alkyl, or hydroxy alkyl group, with at leastone of the X substituents being a hydroxy alkyl group of the structure--(CH₂)_(n) OH, wherein n is 1 to 3; and, (b) from 0.25 to 4 parts byweight of an oil-soluble acylated nitrogen compound having a numberaverage molecular weight ranging from about 1,300 to 8,000 characterizedby the presence within its structure of a substantially saturatedhydrocarbon-substituted polar group selected from the class consistingof acyl, acylimidoyl, and acyloxy radicals wherein the substantiallysaturated hydrocarbon substituent contains at least about 50 aliphaticcarbon atoms and a nitrogen-containing group characterized by a nitrogenatom attached directly to said polar radical.
 2. A composition accordingto claim 1 wherein said combination is present in from about 0.05 to 10wt. % based on the total weight of said composition, said hydrocarbylsubstituted dicarboxylic acid material is poly(alkenyl)succinicanhydride with said poly(alkenyl) substituent having a number averagemolecular weight of from about 900 to about 2800, said substantiallysaturated hydrocarbon-substituted polar group is poly(alkenyl)succinicanhydride with said poly(alkenyl) substituent having a number averagemolecular weight of from about 900 to about 2800 and saidamino-1-alkanol is tris-(hydroxymethyl) aminomethane and said nitrogencontaining group being an alkylene polyamino substituent having from 2to 60 carbon atoms and from 2 to 6 nitrogen atoms.
 3. A compositionaccording to claim 2 wherein said oxazoline reaction product containsfrom 0.1 to 2 weight percent of zinc and said acylated nitrogen compoundcontains from 0.3 to 0.9 weight percent boron.
 4. A compositionaccording to claim 2 wherein both said poly(alkenyl) substituents have a(M_(n)) of from about 1100 to about 2000, said oxazoline reactionproduct has a (M_(n)) ranging from 1200 to 3100, said acyl nitrogencompound has a (M_(n)) ranging from 2000 to 6000, and said oilcomposition contains from about 0.05 to 10 wt. %, based on the totalweight of said composition of said combination which consists of onepart by weight of (a) to from about 1 to 3 parts by weight of (b).
 5. Acomposition according to claim 4 wherein said oxazoline reaction productis obtained from the reaction of one molar proportion of a poly(butenyl)C₄ -C₁₀ monounsaturated dicarboxylic acid material with saidpoly(butenyl) substituent having (M_(n)) of about 1300 and about twomolar proportions of said tris(hydroxymethyl) aminomethane at atemperature of from about 160° C to about 220° C. until cessation ofwater evolution and said acyl nitrogen compound is obtained from thereaction of about two molar proportions of a poly(butenyl) substitutedsuccinic anhydride material with said poly(butenyl) substituent having a(M_(n)) of about 1300 with about one molar proportion of tetraethylenepentamine at a temperature of from about 140° C. to about 165° C. untilabout 2 molar proportions of water has evolved followed by condensationwith boric acid at a temperature of from about 135° C. to about 165° C.6. A concentrate comprising from about 10% to about 90% by weight ofmineral oil and from about 10% to about 80% by weight of the dispersantcombination of: (a) a bis-oxazoline of poly(isobutenyl) succinicanhydride having a (M_(n)) of about 1700; and, (b) a borated alkylenepolyamino-diimide of poly(isobutenyl) succinic anhydride having a(M_(n)) of about 3400, the weight ratio of (a) to (b) ranging from about1 to 3.